In most automobiles and other automotive vehicles in present-day use, many of the auxiliary current consuming devices are connected to the battery through independent circuits. Therefore, it is possible for the operator to leave the vehicle with, for example, the headlights, radio, or other accessories in an energized condition. This can produce a severe drain on the battery of the vehicle, and it is a common experience for a person to return to his automobile after such an occurrence and find the battery dead, or in a seriously low state of charge.
Control systems have been proposed in the past for automatically disconnecting the current consuming devices of an automobile from the battery. However, in some instances, these prior art systems have proven themselves to be complicated in their construction and awkward to install in the electrical system of existing motor vehicles. In other instances, it has been found that the prior art control systems of this type often operate at times when their operation is not desired.
For example, one known prior art control system automatically disconnects the current consuming devices whenever the driver leaves the driver's seat of the motor car. This, however, can prove awkward in situations where the driver wishes merely to step out of the car for a moment, to close his garage doors or to check some other item. At such times, he does not want his headlights, and other instrumentalities in the car to be turned off.
Another prior art control system automatically turns off the electrical system of the vehicle whenever the engine temperature drops below a particular level. This is a convenient system in that it provides an appreciable time lag before it operates, so that the operator can leave the vehicle for short intervals without the electrical accessories being de-energized. However, this type of prior art system is relatively expensive, and is difficult to install.
The control system of the present invention is so conceived, and its various components are so related, and they cooperate with one another in such a manner, that the control system operates only when it is wanted. As will be described, the system of the invention is constructed to sense when the ignition switch is off, and when the generator is inoperative, and it then functions to monitor the discharge current of the battery. If the discharge current is higher than what would normally be sufficient, for example, to run a clock or other continuously energized electric device in the car, the control system operates to turn off the electrical system of the motor car, or at least to reduce the current drain to a lower level. A timer is included in the control system of the invention, to provide a predetermined time delay before the system will operate, for the reasons explained above.